1. Field of the Invention
The present invention relates to an electrophotographic developing agent. More particularly, the invention relates to an electrophotographic developing agent having improved fusing property and image gloss, etc. while ensuring durability by combining a high viscosity polyester resin with a low viscosity polyester resin.
2. Description of the Related Art
Electrophotographic image processing apparatuses, such as laser printers, facsimiles, copying machines, and the like are now widely used. The apparatuses form desired images by forming latent images on a photoreceptor by utilizing a laser, transferring a toner to the latent images on the photoreceptor using an electrical potential difference, and then transferring the images to a printing media such as paper.
Recently, image forming apparatuses, such as laser beam printers (LBPs) for electrophotographs, multifunction machines, color copying machines, and the like are widely used and there is a need to increase image qualities of the apparatuses. Color laser printers realize various colors using four basic color toners (cyan, magenta, yellow, and black), unlike mono-color laser printers. For example, magenta and yellow are used together to realize a red color. Thus, color laser printers form thicker image toner layers than mono-color laser printers. Color printers need a higher fusing property than mono laser printers to maintain a fusing property of the thicker toner layers on the toner images.
There is a great need for double-sided print to reduce an amount of paper used in view of environmental problems and to meet users' needs. Double-sided print has a greater risk of contamination of back sides due to hot offset and a greater risk of serious wrap jamming of a fusing unit, than one-sided print. In order to solve these problems, releasing agents are kneaded and dispersed into toners. However, there are many difficulties in selecting suitable kneading conditions and types of the releasing agents.
In case of mono-color prints, non-gloss prints are preferred to prevent fatigue of eyes due to dazzle and to facilitate copying. However, as expectations for graphics and real picture print increases according to colorization, there is an increasing need for high gloss prints such as photographs.
In many toners having a high gloss, the durability and image qualities deteriorate as the time of use increases. Many trials have been conducted to overcome these problems.